Expansion panels are provided in known bottles blow moulded in polymeric material because the bottle neck and cap do not permit flexure to accommodate pressure changes in a bottle. Examples of plastics bottles having expansion panels in their side wall are described and shown in European patent application Published No. 0279628 (YOSHINO KOGYOSHO) and British patent application Published No. 2188272. In both these publications the bottle has a neck supported on a shoulder which connects to a substantially cylindrical body portion that is provided with a plurality of flexible panels each joined to the next by a column shaped rib extending approximately half the height of the bottle. These complicated shapes are easily achieved by blow moulding of thermoplastic material but difficult to achieve on a metal can body because the metal has limited ductility and stiffer nature. Both these prior art bottles have an array of annular beads in the shoulder or upper part of the body and this "hooped" zone cannot contribute to the desired expansion of container volume and detracts from columnar strength required to support axial loading that arises when bottles are stacked on pallets.
In European patent application, Published No. 0246156 (The Fresh Juice Company) a bottle of square cross section is blow moulded from high density polyethylene to comprise a neck supported by a shoulder which connects with an upper annulus of square section having smooth surfaces, and a lower annulus connected to the top annulus by a recessed body portion which includes an elliptical flexible panel in each rectilinear face. Mass produced cans for processed foods and beverages are usually made cylindrical because round can ends are easier to attach to the sidewall by means of a double seam than are rectangular cans such as are used for corned beef tins. The expansion panels in this publication are not such as would permit substantial inward flexing of a metal can during processing of a food product.
EP 0068334 (TOPPAN PRINTING CO) describes a cylindrical paper container body that may include a metal foil layer. The cylindrical side wall has cylindrical portions, at each end, which are joined by a plurality of longitudinal panels each joined to the next by a linear crease line. Each panel is convex initially and pressed to a flat configuration after filling of the container while the contents cool. Whilst the paper materials described are able to tolerate creasing, metallic side wall materials of stiff temper, such as temper 4 steel or wall ironed side walls may be cracked by sharp crease lines. Furthermore, the rolling operation after filling is not desirable.
British Pat. No. 703836 (FRANGIA) describes metal containers having a side wall integral with an end wall. The side walls described include tapered side walls and substantially cylindrical side walls but other shapes, such as rectangular or oval, are also shown. In each example the side wall comprises a peripheral flange; a cylindrical portion dependent from the interior of the flange; a body portion dependent from the cylindrical portion and comprising a great number of convex ribs and concave grooves forming a sinusoidal profile; and a second cylindrical portion connected to the end wall.
Although the purpose of the ribbed body portion is not explained it is believed that these ribs and grooves are to provide strength against a load applied axially to the containers, as would arise when filled containers are stacked. The ribs and grooves provide strengthening of the container and have too small a circumferential extent in relation to the thickness of the container wall to permit substantial flexing during processing a food product.